1. impossible to break through, penetrate, or overcome

Examples

• The castle’s walls were considered unbreachable by enemy forces.
• She maintained an unbreachable silence about the incident.
• The security system created an unbreachable barrier around the facility.
• His unbreachable confidence impressed everyone in the room.
• The treaty established unbreachable borders between the two nations.
• The firewall provided unbreachable protection against cyber attacks.